An internal combustion engine is used as a power plant of a vehicle drive unit for an automobile. As for a spark-ignited internal combustion engine, it is equipped with a throttle and an ignition system as actuators for regulating the torque. A throttle can be used to regulate torque by controlling an intake air amount. An ignition system can be used to regulate torque by an ignition timing.
There exist both advantages and disadvantages about each actuator. If a throttle and an ignition system are taken for examples, the advantage of the ignition system while comparing with the throttle is in its superior torque response to an operation. However, there also exists a disadvantage of giving high impact on fuel consumption, an exhaust gas characteristic, a knock characteristic or the like about an ignition system. Thus, in order to realize a desired torque while keeping basic characteristics required for a vehicle drive unit such as fuel consumption at a high level, it is necessary to operate each actuator adequately in accordance with an individual characteristic thereof.
Conventionally, the art disclosed in Japanese Patent Laid-Open No. Hei6-207571, for example, is known as an art for regulating engine torque by making two actuators with different characteristic collaborate. The art disclosed here makes a throttle and an ignition system collaborate so that the torque of the internal combustion engine can follow rapid increase of target torque at the time of a gear shifting operation. More specifically, at the time of the gear shifting operation, the throttle is opened before the target torque is increased so that the intake air amount is increased in advance of an increase of the target torque. Also, the system in the art cancels the torque change with an increase of the intake air amount by retarding the ignition timing at the same time the throttle is opened. Then, from the time the target torque is increased, the intake air amount is further increased while the retarded ignition timing becomes returned.